The present invention relates to copolymers of one or more C2-8 alpha olefins with one or more C8-20 vinyl aromatic monomers, in which the vinyl aromatic monomer is incorporated into the polymer in a manner such that the distribution of vinyl aromatic monomer does not follow a Bernoullian statistical distribution and not less than 90% of the vinyl aromatic monomer is in the form of triads of the structure of C2-8 alpha olefin-vinyl aromatic monomer xe2x80x94C2-8 alpha olefin as determined by 13C NMR.
U.S. Pat. No. 6,066,709 issued May 23, 2000 assigned to Denki Kagaku Kogyo, Kabushiki discloses an ethylene styrene copolymer having from 1 to 55 mole % of an isotactic ES alternating structure having a head to tail bond structure (e.g. ESSE). The polymers of the current invention do not have an ethylene and a styrene monomer in alternating manner.
U.S. Pat. No. 6,191,245 issued Feb. 20, 2001, to Campbell et al, assigned to the Dow Chemical Company teaches copolymers of one or more alpha olefins and one or more vinyl aromatic monomers which are substantially random (Col. 6, lines 45-48) containing head to tail insertion (ESSE). Analysis of the polymers of the current invention indicates over 90% of the styrene monomer is isolated and separated by not less than 5 methylene units (in case of ethylene styrene copolymer).
U.S. Pat. No. 5,703,187 issued Dec. 30, 1997, assigned to the Dow Chemical Company teaches pseudo random co-polymers of styrene and ethylene. In the polymers at the present invention the aromatic branches are separated of either 5 or 6 methylene (CH2) units (e.g. EESEES (5 CH2 between branches) or EES (reverse styrene-6 methylene groups between branches). The Dow Patent does not teach this.
There are a number of Idemitsu Kosan Co. Ltd. patents which teach polymers comprising blocks of syndiotactic polystyrene (the phenyl rings are alternating on opposite sides of the backbone) and the olefin is incorporated in repeating units (e.g. olefin blocks). The patent teaches blocks of syndiotactic polystyrene and does not suggest the isolated vinyl aromatic structure of the present invention. Additionally, the process for preparing the block copolymers does not use the catalyst system contemplated by the present invention.
U.S. Pat. No. 6,239,242 B1 issued May 29, 2001 discloses pseudo block polymers of vinyl aromatic monomers and alpha olefins. At least 10 weight % of the vinyl aromatic monomers are incorporated in the form of at least one or more atactic pseudo blocks (three or more vinyl aromatic monomers in conjunction). In the polymers of the present invention the vinyl aromatic monomers are isolated. There are no blocks or pseudo blocks of the vinyl aromatic monomers.
U.S. Pat. No. 3,390,141 issued Jun. 25, 1968 teaches a block copolymer of styrene and ethylene containing from 0.01 to 7 weight % of styrene block polymerized in the presence of a conventional Ziegler-Natta polymerization system. The patent teaches that the styrene is not incorporated into the ethylene backbone of the polymer but rather tends to be in styrene blocks at the end of the olefin homopolymer (Col. 2 lines 55-60). This teaches away from the subject matter of the present patent application as the vinyl aromatic monomer is incorporated into the backbone of the polymer. Further, in the polymers of the present invention the vinyl aromatic monomer is not incorporated in the form of blocks. Rather the vinyl aromatic monomers are separated by 5 or 6 methylene units.
U.S. Pat. No. 5,652,315 issued Jul. 29, 1997 to Inoue et al. assigned to Mitsui Toatsu Chemicals, Inc. teaches the polymerization of an ethylene styrene interpolymer which is substantially random in the presence of a bridged bis cyclopentadienyl transition metal compound in the presence of aluminoxane as an activator. The process of the patent requires the presence of a bridging moiety which has been eliminated in the present invention. Further the polymers of the patent are substantially random. The polymers of the present invention are not substantially random in that they do not have a Bernoullian distribution of monomers. Rather the vinyl aromatic monomers are separated by 5 or 6 methylene units.
The present invention provides a polymer comprising from 95 to 80 weight % of one or more C2-8 alpha olefins; from 5 to 20 weight % of one or more C8-20 vinyl aromatic monomers which are unsubstituted or substituted by one or more substituents selected from the group consisting of a chlorine or bromine atom and a C1-4 alkyl radical; and from 0 to 10 weight % of one or more monomers selected from the group consisting of C5-9 nonconjugated diolefin monomers wherein the vinyl aromatic monomer is incorporated into the polymer in a manner such that the distribution of vinyl aromatic monomers does not follow Bernoullian statistical distribution and not less than 90 % of the branching due to the vinyl aromatic monomer is separated by 5 or 6 methylene groups as determined by 13C NMR.
The present invention further provides a process for preparing the above interpolymer comprising contacting a monomer mixture comprising from 0.5 to 0.7 mole fraction of one or more C8-20 vinyl aromatic monomer which are unsubstituted or substituted by one or more substituents selected from the group consisting of C1-4 alkyl radicals; from 0.5 to 0.3 mole fraction of one or more monomers selected from the group consisting of C2-8 aliphatic alpha olefins and optionally from 0 to less than 0.1 mole fraction one or more monomers selected from the group consisting of C5-9 nonconjugated diolefins with a catalyst comprising a phosphinimine compound of the formula;
Cp((R1)3Pxe2x95x90N)xe2x80x94Mxe2x80x94L2
wherein each R1 is independently selected from the group consisting of C3-6 alkyl radicals which are unsubstituted or substituted by a heteroatom, provided that there is a carbon phosphorus bond and the CPN bond angle is less than 108xc2x0, Cp is selected from the group consisting of a cyclopentadienyl, indenyl and fluorenyl radicals which are unsubstituted or substituted by one or more substitutents selected from the group consisting of C1-6 alkyl radicals which are unsubstituted or substituted by one or more fluorine atoms; M is selected from the group consisting of Ti, Zr, and Hf, and each L is independently selected from the group consisting of a halogen atom, a hydrogen atom, a C1-10 alkyl radical, a C1-10 alkoxide radical, and a C6-10 aryloxide radical, and at least one activator, at a temperature from 25xc2x0 C. to 150xc2x0 C. and a pressure from 15 psi to 15,000 psi.